1. Field of the Invention
This invention relates in general to a serial printer which includes a rotatable print wheel. More particularly, this invention relates to a serial impact printer which serrates a check or other document with a protected amount field. Still more particularly, this invention relates to a serial print wheel engine for use as the protect amount print station of a check writer.
2. Description of the Prior Art
Serial printers which include a print element in the shape of a disk or cup are known in the art. In general, such printers can be divided into two types. In the first type, the print element is constantly rotating and printing takes place on the fly. In the second type, the print element stops and starts and printing takes place while the print element is stationary.
An example of a serial printer with a constantly rotating print element can be found in U.S. Pat. No. 3,461,235 (Wilcox). Examples of a serial printer with a print element that stops before printing occurs can be found in U.S. Pat. Nos. 3,707,214 (Panzo) and 4,037,707 (Ku).
Serial print elements where the print element is in the shape of a cup are also known. For example, U.S. Pat. No. 3,640,369 (Rolph) shows a print element with a cup-shaped shell having integrally formed characters on the outer surface of the shell.
In U.S. Pat. No. 4,037,707 (Ku), the sides of a cup shaped print element are formed by a plurality of fingers, each of which has a number of characters. A hammer is located in the center of the cup. Printing is accomplished by rotating the cup so that the desired finger is located between a hammer and the paper. The hammer is then fired to print the desired character.
In the cited prior art references, the hammer utilized to depress the characters against the paper provides sufficient pressure to accomplish normal printing. However, the hammer pressure is insufficient to enable the print characters to serrate the paper in the manner required to produce a protected amount field on a check or other document.